Can sibilance be eliminated?

Yes, assuming the negative sibilance is not in the recording itself, it can be entirely eliminated through proper AC line conditioning assuming you have a certain caliber of components.

Although vibration and resonance control can perform wonders in and of itself, I do not agree at all with the statement that vibration or resonance control having anything to do with inducing negative sibilance into a playback system.

-IMO

I've found the worst of the sibilance can be decreased or eliminated via careful controlling of room reflections and power conditioning.

Some questions & comments:

Why would you completely want to remove all sibilance? It is a natural byproduct of certain vocal output and occurs fairly often in "real life". Probably the base-line here should be to set expectations correctly - if the sibilance is accurately recorded in your program material you probably want it accurately reproduced - no?

Next, are your speakers properly set up & calibrated? That's the first thing to attend to. Sibilance reportedly/typically occurs in the 5-10KHz range, so if your speakers are peaking in the upper ranges (including maybe even higher than 10K) that could contribute mightily. That's probably the #1 thing to check out.

Room (reflections, etc.) is probably next. Since your speakers are what makes the sound and the whole room environment (including speaker placement) is the next-most significant thing that affects what sound(s) reach your ears then that's the next place to focus. Little things, like "is there a flat-topped coffee table between you & the speakers?" may contribute significantly to what's reaching your ears in your listening position. You can find a wealth of material on room factors at Rives, etc. that may help.

If you plan on keeping your speakers, etc. then all that stuff above is the stuff that matters most. Cables and power cords and conditioners and all that other "stuff" have such an infinitesimal impact on the sounds you hear, when compared to speakers & room environment & source material, that you can pretty much de-prioritize those things until you have your speakers and room tamed. As usual, JMO & YMMV...

As others have said, most sibilance is in the source recording. Different types and brands of microphone produce recordings that are dramatically different, and some are better than others with regard to sibilance.
Try playing back the record at reduced volume level. Problems caused by your playback system will generally increase with volume. It the problem persists at all playback levels, it is probably in the recording.

Marakan hit the nail on the proverbial head. Audiophiles are gladly ignoring that the chain starts with the recording and that they actually have very little control over many aspects of the sound reproduced by their system. Mr. hosehaed is also so right in his statement that sibilance is, often enough, part and parcel of a singers instrument and delivery.